Current link mode values do not allow to enable packed pixel modes.

Select packed pixel clock mode, if needed, every time the link mode
register gets updated.
Signed-off-by: Maciej Purski <m.purski@samsung.com>
Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1530204243-6370-4-git-send-email-m.purski@samsung.com